XCode 8 奇怪的操场错误,无法查找符号 [英] XCode 8 strange Playground error, Couldn't Lookup Symbols
问题描述
我试图在 Xcode 8 的 Playground 中使用自动布局.但是,一旦我添加了该行,我就开始收到此错误:
I was trying to use auto layout in a Playground on Xcode 8. However, as soon as I added the line, I started receiving this error:
Playground execution failed: error: Couldn't lookup symbols:
__TWPCSo6UIView17PlaygroundSupport22PlaygroundLiveViewableS0_
__swift_FORCE_LOAD_$_swiftCoreGraphics
__swift_FORCE_LOAD_$_swiftDarwin
__TMaC17PlaygroundSupport14PlaygroundPage
__swift_FORCE_LOAD_$_swiftObjectiveC
__swift_FORCE_LOAD_$_swiftUIKit
_playground_log_hidden
_playground_logger_initialize
__swift_FORCE_LOAD_$_swiftCoreImage
__swift_FORCE_LOAD_$_swiftDispatch
__TFC17PlaygroundSupport14PlaygroundPageau7currentS0_
__swift_FORCE_LOAD_$_swiftFoundation
__TFC17PlaygroundSupport14PlaygroundPages8liveViewGSqPS_22PlaygroundLiveViewable__
* thread #1: tid = 0x14b6b4, 0x000000010f2f43c0 MyPlayground`executePlayground, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2
* frame #0: 0x000000010f2f43c0 MyPlayground`executePlayground
frame #1: 0x000000010f2f39c0 MyPlayground`__37-[XCPAppDelegate enqueueRunLoopBlock]_block_invoke + 32
frame #2: 0x000000010fe0c89c CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
frame #3: 0x000000010fdf1944 CoreFoundation`__CFRunLoopDoBlocks + 356
frame #4: 0x000000010fdf10b5 CoreFoundation`__CFRunLoopRun + 901
frame #5: 0x000000010fdf0ad4 CoreFoundation`CFRunLoopRunSpecific + 420
frame #6: 0x000000011518aa61 GraphicsServices`GSEventRunModal + 161
frame #7: 0x0000000110996de4 UIKit`UIApplicationMain + 159
frame #8: 0x000000010f2f36e9 MyPlayground`main + 201
frame #9: 0x00000001132e068d libdyld.dylib`start + 1
我不知道这是什么意思.我的意思是,我的解释是 Xcode 找不到像 UIKit 这样的库,但我知道事实并非如此,因为我使用了 UIKit 并且很好,直到那条自动布局使派对崩溃.源代码真的很小,所以我把它完整地包括在内:
I have no idea what this means. I mean, my interpretation is that Xcode can't find libraries like UIKit, but I know that is not the case, as I used UIKit and such fine until that line of auto layout crashed the party. The source code is really small, so I am including it in its entirety:
import UIKit
import PlaygroundSupport
let view = UIView(frame: CGRect(x: 0, y: 0, width: 500, height: 500))
view.translatesAutoresizingMaskIntoConstraints = false
view.backgroundColor = UIColor.white
PlaygroundPage.current.liveView = view
let field = UITextField(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
field.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 1).isActive = true
field.backgroundColor = UIColor.red
view.addSubview(field)
源代码底部的第三行似乎是导致问题的原因.这是我搞砸了还是测试版错误?我迷路了.
The third line from the bottom of the source seems to be causing the problem. Is this something that I messed up or is it a beta bug? I'm lost here.
推荐答案
添加 field
作为 view
的子视图,然后设置约束.为不在同一视图层次结构中的视图添加约束时会引发异常.
Add field
as a sub view of view
then set your constraints. There is an exception that is raised when constraints are added for views not in the same view hierarchy.
例如:
import UIKit
import PlaygroundSupport
let view = UIView(frame: CGRect(x: 0, y: 0, width: 500, height: 500))
view.backgroundColor = UIColor.white
PlaygroundPage.current.liveView = view
let field = UITextField(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
view.addSubview(field)
field.translatesAutoresizingMaskIntoConstraints = false
field.widthAnchor.constraint(equalTo: view.widthAnchor, multiplier: 1).isActive = true
// add the rest of your constraints
field.backgroundColor = UIColor.red
您通常还需要调用 view.layoutIfNeeded()
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